1. Field of the Invention
The present invention relates to a camera capable of detecting information about the kind of illumination light source used during photography and recording the result of the detection on a photographic film.
2. Description of the Related Art
For example, Japanese Patent Publication No. Sho 58-53327 discloses a camera which is arranged to detect whether the kind of light source used during photography is natural light (sunlight or daylight), a fluorescent lamp or a tungsten lamp, and record the result of the detection on a film as an optical mark.
FIG. 38 is a schematic, front elevational view showing a conventional film on which information about a light source is recorded.
During photography, illumination light is received by a pair of filter and light-receiving elements which have a spectral characteristic showing a peak in an infrared range or a visible light range close thereto as well as a pair of filter and light-receiving elements which have a spectral characteristic showing a peak in an ultraviolet range or a visible light range close thereto. The outputs from the respective pairs which have received the illumination light are compared with each other, and if the amount of received light is larger in the infrared range than in the ultraviolet range, it is determined that the kind of light source is a tungsten lamp. If the kind of light source is not a tungsten lamp, the rectified outputs of the respective pairs are compared with each other and it is determined whether the kind of light source is natural light or a fluorescent lamp, by utilizing the knowledge that a rectified level obtained from the fluorescent lamp becomes lower by the amount of flicker. Three LEDs which respectively correspond to the results of the aforesaid decisions as to illumination light are used to record an imprinting code co at a position independent of both a frame fa of a film f and perforations fp, as shown in FIG. 38.
To produce a print from such film f after development, the imprinting code co is read out by a printer and a printing filter is adjusted according to the kind of illumination light source, thereby effecting appropriate correction of color balance. In this manner, it is possible to eliminate the problem that if a general daylight type of negative film is used to photograph a person under fluorescent illumination, the skin of the photographed person is printed in greenish flesh.
As another conventional means for detecting the kind of illumination light source, Japanese Laid-Open Patent Application No. Hei 3-136026 discloses a camera arranged to detect the color temperature of an illumination light source by using an RGB sensor, convert the color temperature into a color temperature code and record the color temperature code on a film. During printing, the color temperature code is read out to effect correction.
Japanese Laid-Open Patent Application No. Hei 3-163538 discloses a camera arranged to detect the presence or absence of a bright line of 436 nm or 546 nm which is peculiar to a fluorescent lamp, thereby determining whether the kind of illumination light source is a fluorescent lamp.
However, none of the aforesaid conventional examples discloses measures against the problem that the camera may make an erroneous decision as to the kind of light source and record erroneous information on a film. The decision processing proposed by any of the conventional examples is, therefore, imperfect.
FIG. 14 is an explanatory view showing the status in which a decision is made as to the kind of light source by means of a conventional arrangement. As shown specifically in FIG. 14, a camera C is arranged to detect the color of a light source within the extent of a light-receiving angle .theta. and make a decision as to the kind of light source. Since a person 0 who is a subject is illuminated with natural light S, the camera C needs to determine that the kind of light source is natural light. However, if a considerably wide area of a background B has a particular color, the camera C will be influenced by the background B. For example, if the background B is green, the camera C will determine that the kind of light source is a fluorescent lamp. This status is generally referred to as the "color-failure scene".
If a tungsten lamp L is located behind the subject O, the camera C will be influenced by the tungsten lamp L and erroneously determines that the kind of light source is a tungsten lamp.
If such an erroneous decision result is recorded on the film without modification and printing conditions for a printer are set on the basis of the recorded data, the color balance of the obtained print will be seriously impaired.
FIG. 39 shows the photographic status in which the person O who is a subject stands near a window W of a room R and the room R is provided with a fluorescent lamp FL as an illumination light source. In such a photographic status, the subject O is illuminated with two kinds of light sources, the natural light S which enters from the window W and illumination light F emitted from the fluorescent lamp FL. Such a scene is generally referred to as the "mixed-illuminant scene". In the case of the mixed-illuminant scene, even if the kind of light source is recorded on the film as fluorescent lamp "F" or natural light "D", it is impossible to produce a good print. In other words, if color correction and print-exposure correction are performed by a method optimum for a particular kind of light source before a print is produced from a frame which contains a photographed subject illuminated with two or more kinds of light sources, the color balance and the amount of print exposure are unnaturally corrected to impair the printing quality of the frame. The above-described problem derived from the mixed-illuminant scene takes place in the printing of various mixed-illuminant scenes illuminated with fluorescent light and tungsten light, natural light and tungsten light, and others.
To prevent the camera C from erroneously determining that the kind of light source is the fluorescent lamp "F", it is necessary to prepare a decision region for detecting a photographic scene illuminated with a fluorescent lamp which emits light containing large amounts of green components and a decision region for detecting a photographic scene illuminated with natural light having natural color, as well as a decision region for detecting a color-failure scene which is slightly greener than natural color. However, there have not yet been disclosures which suggest measures to be taken against the color-failure scene, the mixed-illuminant scene or other similar scenes illuminated with an unknown kind of light source. As is apparent from the above description, there is the problem that it is impossible to make an accurate decision by using the decision processing of making a decision as to the kind of light source in accordance with the conventional three categories, namely, fluorescent light, tungsten light and natural light.